A wide variety of machines have been available in the past for use in maintenance of surfaces such as floors, parking lots, and the like. Such maintenance machines include self-propelled riding machines as well as self-propelled walk behind machines. Typically, both types of machines have utilized fans or pumps to draw a vacuum in the brush housing thereby minimizing dusting around the brush housing. Filters have generally been provided to minimize the amount of dust that passes through the fan. In the absence of such filters, the dust causes unnecessary wear and degradation of the fan and pollutes the atmosphere. A long-standing problem has been the accumulation of dust on the filter. This tends to block the filter and create a substantial pressure differential between the upstream side of the filter and the downstream side of the filter, thus reducing the efficiency of the equipment. A manual or mechanical system is generally incorporated to clean the filter at regular intervals to enable the machine to continue to function without frequent replacement of the filter.
Walk behind units desirably are of a small size and thus large powered hopper dumping elements have not been provided. Some walk behind units have included a hopper that may be manually lifted by the operator, carried to a suitable location and dumped. Such units in the past have, of necessity, spaced the filter from the hopper to permit removal of the hopper. Such spacing, of course, does not provide for a minimized size of unit. Further, such spacing does not provide for return of the dust from the filter to the hopper. Instead, such units have generally included a secondary hopper or drawer into which accumulated dust is dropped.